1. Field of the Invention
The present invention relates generally to a method and an apparatus for extruding a viscous fluid and, more specifically, to a method and an apparatus for extruding a highly or ultrahighly viscous fluid from a tank. The method and apparatus of the present invention are characterized by extruding the highly or ultrahighly viscous fluid from the tank and by cleaning the apparatus after the extrusion operation.
2. Background Information
In the production of a highly viscous or an ultrahighly viscous fluid such as ink, a coating material, a pigment, a sealing agent, a caulking agent or an adhesive, the removal of such a fluid from a stirring tank is difficult to accomplish due to the poor fluidity of the fluid. For such reason, a method and an apparatus have been used wherein after a stirring process, a pressing plate is fitted inside of the tank, and the pressing plate is moved toward the bottom of the tank to pressurize the highly viscous fluid in the tank, thereby extruding the fluid from an ejecting port or outlet disposed at the bottom of the tank.
In the foregoing extrusion method and apparatus, the pressing plate is hermetically fitted inside of the tank so that the pressing force will be securely effected on the highly viscous fluid in the tank. When the pressing plate is fitted inside of the tank, a layer of air may sometimes be present between the highly viscous fluid and the pressing plate. When such layer of air is present, the pressing force of the pressing plate is effected on the highly viscous fluid through the layer of air, whereby the extrusion operation becomes highly difficult to achieve. Furthermore, after the termination of the extrusion operation, when the pressing plate is pulled up (i.e., removed from the tank), since the interior of the tank is in an approximate vacuum state, it is extremely difficult to remove the pressing plate from the tank. Furthermore, if the highly viscous fluid remains adhered to or clogged in the outlet of the tank and/or in valves or pipes connected to the outlet of the tank, a tank cleaning operation becomes laborious and time consuming. Such laborious and time consuming cleaning operation lowers the efficiency of the extrusion method and apparatus, thereby rendering difficult the production of different types of products such as, for example, producing different color ink products.